Modified wollastonite as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of inorganic powder preparation, and provides modified wollastonite as well as a preparation method and application thereof. The method comprises the following steps: mixing wollastonite, an inorganic silicon source and water, and grinding to obtain wollastonite slurry; the precipitated white carbon black solution and the sodium polyacrylate solution are mixed and ground, and white carbon black slurry is obtained; the wollastonite slurry and the white carbon black slurry are mixed and ground, and mixed slurry is obtained; mixing the mixed slurry with an organic dispersant, and grinding to obtain composite powder; the composite powder and a silane coupling agent are mixed for modification, and modified wollastonite is obtained. According to the invention, a particle compounding method is selected, wollastonite and precipitated white carbon black are respectively used as raw materials to prepare the composite particle material with the wollastonite surface coated with white carbon black, the bottleneck problem of weak binding force between fluororubber and an inorganic material is solved, the high-temperature compression permanent deformation and thermal conductivity of fluororubber are improved, and the service life of the fluororubber is prolonged. And localization of the wollastonite filler with high performance and high added value is realized.

Description

Technical Field

[0001] The invention relates to the technical field of inorganic powder preparation, and in particular to modified wollastonite and a preparation method and application thereof. Background Art

[0002] Fluororubber is a synthetic polymer elastomer with excellent properties such as high temperature resistance, oil resistance, and chemical resistance. It is an important raw material for strategic emerging industries such as new energy, new materials, energy conservation and environmental protection, and is widely used in cutting-edge technology fields such as national defense, aerospace, electronic communications, vehicles and ships, and petrochemicals. However, the shielding effect of fluorine atoms on the carbon chain makes it difficult for fluororubber to be perfectly combined with other fillers. This has led to the long-term reliance of fillers used in the fluororubber industry on imported products such as wollastonite, diatomaceous earth, and kaolin, which are expensive, unstable in supply chain, and high in transportation costs. At the same time, although fluororubber has excellent heat resistance, the tensile and tear strength of fluororubber will significantly decrease with increasing temperature, and the mechanical properties will decrease significantly at high temperatures, further limiting the application of fluororubber under high temperature conditions. Therefore, it is crucial to find a high-temperature resistant and chemically stable filler for use in fluororubber and solve the interface compatibility problem between fluororubber and functional fillers to broaden the application of fluororubber in the field of functional materials.

[0003] Wollastonite is a chain silicate mineral with the chemical formula of CaSiO3. It is a white radial and fibrous aggregate with the characteristics of insulation, heat resistance (1200℃), stable chemical properties, alkali resistance, and corrosion resistance. Its Mohs hardness is 4.5-5. Its special structure and hardness make it a filling and reinforcing role in rubber, which can effectively improve the wear resistance and durability of rubber products. However, due to the high hardness of wollastonite, it is difficult to ultrafine it using traditional mechanical grinding processes and it is easy to destroy its fiber structure. At the same time, there are a large number of hydroxyl groups on its surface, and the interface interaction with polymers is weak, which easily leads to a significant decrease in the mechanical properties of polymer materials, limiting its application in high-precision and other industrial fields. Precipitated silica is often used in natural rubber, styrene-butadiene rubber, nitrile rubber, chloroprene rubber, ethylene-propylene rubber or their blends. The strength of its reinforcement effect on rubber depends on its surface chemical properties and particle size distribution. At present, there are the following problems in the use of precipitated silica in fluorosilicone rubber: first, due to the high degree of particle aggregation of precipitated silica, its reinforcing effect on rubber is not as good as that of fumed silica; second, due to particle agglomeration, the silica particles inside the agglomerate do not actually play a role; finally, silica particles are fine and light, and have strong fluidity and splashing in the air, making it difficult to mix evenly with resins and other inorganic materials, which restricts the performance of silica and has an adverse effect on the performance of rubber products used. Therefore, improving the reinforcing effect of wollastonite in rubber and solving the problems existing in the application of precipitated silica have become issues that need to be solved urgently. Summary of the invention

[0004] The purpose of the present invention is to overcome the problems existing in the prior art and provide a modified wollastonite and a preparation method and application thereof.

[0005] In order to achieve the above-mentioned object of the invention, the present invention provides the following technical solutions:

[0006] The present invention provides a method for preparing modified wollastonite, comprising the following steps:

[0007] (1) mixing wollastonite, an inorganic silicon source and water and grinding them to obtain a wollastonite slurry;

[0008] (2) mixing the precipitated white carbon black solution and the sodium polyacrylate solution and grinding them to obtain white carbon black slurry;

[0009] (3) mixing and grinding the wollastonite slurry and the white carbon black slurry to obtain a mixed slurry;

[0010] (4) mixing the mixed slurry and the organic dispersant and grinding them to obtain a composite powder;

[0011] (5) mixing the composite powder with a silane coupling agent for modification to obtain the modified wollastonite;

[0012] There is no order restriction between (1) and (2).

[0013] Preferably, the particle size of the wollastonite in step (1) is 5 to 10 μm, and the whiteness of the wollastonite is ≥ 85%;

[0014] The inorganic silicon source in step (1) is sodium silicate or potassium silicate.

[0015] Preferably, the solid content of the wollastonite slurry in step (1) is 60-70%, and the mass ratio of the wollastonite to the inorganic silicon source is 100:0.6-1.2;

[0016] The grinding time in step (1) is 90 to 120 minutes, and the D97 of the wollastonite slurry is 1.5 to 2 μm.

[0017] Preferably, in step (2), the mass fraction of the precipitated silica solution is 25-35%, the mass fraction of the sodium polyacrylate solution is 20-30%, and the mass ratio of the precipitated silica to the sodium polyacrylate solution is 100:6-9;

[0018] In step (2), the main rotating speed of the stirring mill for grinding is 330-390 r / min, the feeding rate of the diaphragm pump for grinding is 40-60 L / min, and the grinding time is 60-90 min.

[0019] Preferably, the mass ratio of the wollastonite slurry to the white carbon black slurry in step (3) is 2.5-3.5:0.5-1.5;

[0020] The main rotating speed of the stirring mill for grinding in step (3) is 450-650 r / min, the grinding ball-to-material ratio is 15-20:1; and the grinding time is 60-90 min.

[0021] Preferably, the organic dispersant in step (4) comprises one or more of polyethylene glycol, a high-efficiency polycarboxylic acid modifier and silicone oil; the mass ratio of the mixed slurry to the organic dispersant is 100:0.8-1;

[0022] The grinding time in step (4) is 60 to 90 minutes, and the D97 of the composite powder is 0.8 to 1.2 μm.

[0023] Preferably, the silane coupling agent in step (5) is N-phenyl-γ-aminopropyltrimethoxysilane coupling agent; and the mass ratio of the composite powder to the silane coupling agent is 100:0.6-1.2.

[0024] Preferably, the modification temperature in step (5) is 80-120° C., and the modification time is 20-60 min.

[0025] The invention also provides modified wollastonite prepared by the preparation method of the modified wollastonite.

[0026] The invention also provides application of the modified wollastonite in fluororubber filler.

[0027] The beneficial effects of the present invention are:

[0028] 1. The present invention provides a method for preparing modified wollastonite, comprising the following steps: (1) mixing wollastonite, an inorganic silicon source and water for grinding to obtain wollastonite slurry; (2) mixing precipitated silica solution and sodium polyacrylate solution for grinding to obtain silica slurry; (3) mixing wollastonite slurry and silica slurry for grinding to obtain a mixed slurry; (4) mixing the mixed slurry with an organic dispersant for grinding to obtain a composite powder; (5) mixing the composite powder with a silane coupling agent for modification to obtain modified wollastonite. The present invention discloses a method for preparing modified wollastonite for high-temperature fluororubber, wherein a particle composite method is used, and wollastonite and precipitated silica are used as raw materials to prepare a composite particle material with silica coated on the surface of wollastonite, thereby solving the bottleneck problem of weak bonding between fluororubber and inorganic materials, improving the high-temperature compression permanent deformation and thermal conductivity of fluororubber, and realizing the localization of high-performance and high-value-added wollastonite filler.

[0029] 2. The inorganic silicon source in step (1) can be used as both a dispersant and an inorganic in-situ modifier, achieving the effect of dispersing and pre-modifying wollastonite, and step (1) utilizes the heat generated in the grinding process to perform dispersion and modification, thereby achieving the effect of energy saving and consumption reduction; in step (3), the needle-shaped wollastonite powder and granular white carbon are compounded, and the white carbon coated wollastonite powder can be filled in the rubber system as a "continuous phase", which can have an excellent filling and reinforcing effect on the rubber and can also have a good thermal conductivity; in step (4), adding an organic dispersant can not only achieve a good modification effect, but also the organic dispersant can be continuously coated on the surface of the powder, achieving a good coating effect; in step (5), a silane coupling agent is used to couple and modify the white carbon coated wollastonite, so that the white carbon coated wollastonite powder has good compatibility with the rubber molecules, further improving the mechanical properties and high temperature resistance of the rubber product. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 The figure is a schematic diagram of a specific process of the preparation method of modified wollastonite in the present invention. DETAILED DESCRIPTION

[0031] The present invention provides a method for preparing modified wollastonite, comprising the following steps:

[0032] (1) mixing wollastonite, an inorganic silicon source and water and grinding them to obtain a wollastonite slurry;

[0033] (2) mixing the precipitated white carbon black solution and the sodium polyacrylate solution and grinding them to obtain white carbon black slurry;

[0034] (3) mixing and grinding the wollastonite slurry and the white carbon black slurry to obtain a mixed slurry;

[0035] (4) mixing the mixed slurry and the organic dispersant and grinding them to obtain a composite powder;

[0036] (5) mixing the composite powder with a silane coupling agent for modification to obtain the modified wollastonite;

[0037] There is no order restriction between (1) and (2).

[0038] In the present invention, the wollastonite in step (1) is preferably needle-shaped wollastonite, and the preparation method of the wollastonite comprises the following steps: coarsely crushing wollastonite ore with a particle size of 1.5 to 6 mm, and then dry grinding to obtain the wollastonite in step (1).

[0039] In the present invention, the coarse crushing and dry grinding are carried out by conventional technical means in the art.

[0040] In the present invention, the particle size of the wollastonite in step (1) is preferably 5-10 μm, more preferably 9-9 μm, and more preferably 7-8 μm; the whiteness of the wollastonite is preferably ≥85%, more preferably ≥87%, and more preferably ≥89%.

[0041] In the present invention, the inorganic silicon source in step (1) is preferably sodium silicate or potassium silicate.

[0042] In the present invention, the solid content of the wollastonite slurry in step (1) is preferably 60-70%, more preferably 62-68%, and more preferably 65-66%; the mass ratio of the wollastonite to the inorganic silicon source is preferably 100:0.6-1.2, more preferably 100:0.8-1.0, and more preferably 100:0.9.

[0043] In the present invention, during the mixing process of step (1), the inorganic silicon source is added in two parts. Specifically, wollastonite, the first part of the inorganic silicon source and water are mixed and a first grinding is performed. After the first grinding is completed, the remaining inorganic silicon source is added and a second grinding is performed to obtain wollastonite slurry.

[0044] In the present invention, the mass ratio of the first part of the inorganic silicon source to the inorganic silicon source in step (1) is preferably 60-70:100, more preferably 62-68:100, and more preferably 65:100; the first grinding time is preferably 30-40 min, more preferably 32-38 min, and more preferably 35 min.

[0045] In the present invention, the grinding time of step (1) (the total time of the first grinding and the second grinding) is preferably 90 to 120 min, more preferably 100 to 110 min, and more preferably 105 to 106 min; the D97 of the wollastonite slurry is preferably 1.5 to 2 μm, more preferably 1.6 to 1.9 μm, and more preferably 1.7 to 1.8 μm.

[0046] In the present invention, the wollastonite slurry obtained in step (1) is dried, and the powder obtained by drying is tested. The specific surface area of ​​the powder is preferably 12 to 14 m 2 / g, more preferably 12.5 to 13.5 m 2 / g, more preferably 13 to 13.2 m 2 / g; the sedimentation volume of the powder is preferably ≥2.7mL / g, more preferably ≥2.8mL / g, and more preferably ≥2.9mL / g.

[0047] In the present invention, the mass fraction of the precipitated silica solution in step (2) is preferably 25-35%, more preferably 27-33%, and more preferably 30%; the mass fraction of the sodium polyacrylate solution is preferably 20-30%, more preferably 22-28%, and more preferably 25%; the mass ratio of the precipitated silica to the sodium polyacrylate solution is preferably 100:6-9, more preferably 100:7-8, and more preferably 100:7.5.

[0048] In the present invention, the purpose of grinding in step (2) is to break up the agglomerated particles of white carbon black. The main speed of the stirring mill for grinding in step (2) is preferably 330-390 r / min, more preferably 350-380 r / min, and more preferably 360-370 r / min; the feeding rate of the diaphragm pump for grinding is preferably 40-60 L / min, more preferably 45-55 L / min, and more preferably 50-52 L / min; the grinding time is preferably 60-90 min, more preferably 70-80 min, and more preferably 75-76 min.

[0049] In the present invention, the mass ratio of the wollastonite slurry and the white carbon black slurry in step (3) is preferably 2.5-3.5:0.5-1.5, more preferably 2.7-3.3:0.7-1.3, and more preferably 3:1; the main speed of the stirring mill for grinding in step (3) is preferably 450-650 r / min, more preferably 500-600 r / min, and more preferably 550-560 r / min; the ball-to-material ratio of the grinding is preferably 15-20:1, more preferably 16-19:1, and more preferably 17-18:1; the grinding time is preferably 60-90 min, more preferably 70-80 min, and more preferably 75-76 min.

[0050] In the present invention, the grinding time, ball-to-material ratio and rotation speed are reasonably controlled to achieve the best composite state of depolymerized silica coated wollastonite, so that wollastonite and silica can be coated and dispersed more evenly.

[0051] In the present invention, the organic dispersant in step (4) preferably comprises one or more of polyethylene glycol, a high-efficiency polycarboxylic acid modifier and silicone oil; the mass ratio of the mixed slurry to the organic dispersant is preferably 100:0.8-1, more preferably 100:0.85-0.95, and more preferably 100:0.9.

[0052] In the present invention, the grinding time in step (4) is preferably 60 to 90 min, more preferably 70 to 80 min, and more preferably 75 to 76 min; after grinding, a composite slurry is obtained, the composite slurry is flash dried, and a composite powder is obtained after cyclone collection; the D97 of the composite powder is preferably 0.8 to 1.2 μm, more preferably 0.9 to 1.1 μm, and more preferably 1.0 μm.

[0053] In the present invention, the silane coupling agent in step (5) is preferably N-phenyl-γ-aminopropyltrimethoxysilane coupling agent; the mass ratio of the composite powder to the silane coupling agent is preferably 100:0.6-1.2, more preferably 100:0.7-1.1, and more preferably 100:0.8-1.0.

[0054] In the present invention, the modification temperature in step (5) is preferably 80-120°C, more preferably 90-110°C, and more preferably 100-105°C; the modification time is 20-60 min, more preferably 30-50 min, and more preferably 40-45 min.

[0055] In the present invention, after the modification is completed, the obtained sample is screened, tested and packaged in sequence using conventional technical means in the art to obtain modified wollastonite.

[0056] The specific process diagram of the preparation method of modified wollastonite in the present invention is as follows: Figure 1 shown.

[0057] The invention also provides modified wollastonite prepared by the preparation method of the modified wollastonite.

[0058] The invention also provides application of the modified wollastonite in fluororubber filler.

[0059] The technical solutions provided by the present invention are described in detail below in conjunction with the embodiments, but they should not be construed as limiting the protection scope of the present invention.

[0060] Example 1

[0061] The wollastonite ore with a particle size of 1.5 to 6 mm is roughly crushed, and then dry-ground to obtain needle-shaped wollastonite with a particle size of 5 to 10 μm and a whiteness of ≥85%;

[0062] Needle-shaped wollastonite, sodium silicate and water were mixed, and the mass ratio of wollastonite to sodium silicate was 100:0.6. During the mixing process, wollastonite, the first part of sodium silicate and water were first mixed and ground for 30 minutes, and then the remaining sodium silicate (the mass ratio of the first part of sodium silicate to all sodium silicate was 65:100) was added and ground for 60 minutes to obtain a wollastonite slurry with a solid content of 65% (the D97 of the wollastonite slurry was 1.8 μm; the wollastonite slurry was dried, and the specific surface area of ​​the dried powder was 13 m 2 / g, sedimentation volume is 2.9mL / g); 30% by mass fraction of precipitated silica solution and 25% by mass fraction of sodium polyacrylate solution are mixed (the mass ratio of precipitated silica to sodium polyacrylate solution is 100:7.5), and ground, the stirring mill host speed of grinding is set to 360r / min, the diaphragm pump feeding rate is 50L / min, and the time is 60min to obtain silica slurry; wollastonite slurry and silica slurry are mixed (the mass ratio of wollastonite slurry to silica slurry is 3:1) and ground, the stirring mill host speed of grinding is set to 550r / min, the ball-to-material ratio is 18:1, and the time is 80min to obtain a mixed slurry; the mixed slurry and polyacrylate are mixed. The mixed slurry and polyethylene glycol (PEG-3350) (the mass ratio of the mixed slurry and polyethylene glycol is 100:0.9) are ground for 60 minutes to obtain a composite slurry. The composite slurry is flash dried and collected by cyclone to obtain a composite powder with a D97 of 1.0 μm. The composite powder is fed to a horizontal gravity infrared mixing modification equipment through a spiral auger, and N-phenyl-γ-aminopropyltrimethoxysilane coupling agent is added (the mass ratio of the composite powder to the silane coupling agent is 100:0.8) for dry composite modification. The modification temperature is set to 100°C and the time is 30 minutes. After the modification is completed, the obtained samples are sieved, tested and packaged in sequence to obtain modified wollastonite.

[0063] The modified wollastonite prepared in this example was subjected to batch sample testing to obtain the physical property parameters of the modified wollastonite obtained in this example, as shown in Table 1.

[0064] Table 1 Physical property parameters of modified wollastonite obtained in Example 1

[0065]

[0066]

[0067] Example 2

[0068] The wollastonite ore with a particle size of 1.5 to 6 mm is roughly crushed, and then dry-ground to obtain needle-shaped wollastonite with a particle size of 5 to 10 μm and a whiteness of ≥85%;

[0069] Needle-shaped wollastonite, potassium silicate and water were mixed, and the mass ratio of wollastonite to potassium silicate was 100:0.8. During the mixing process, wollastonite, the first part of potassium silicate and water were first mixed and ground for 40 minutes, and then the remaining potassium silicate (the mass ratio of the first part of potassium silicate to all potassium silicate was 60:100) was added and ground for 80 minutes to obtain a wollastonite slurry with a solid content of 68% (the D97 of the wollastonite slurry was 1.7 μm; the wollastonite slurry was dried, and the specific surface area of ​​the dried powder was 13.5 m 2 / g, sedimentation volume is 2.8mL / g); 27% mass fraction of precipitated silica solution and 22% mass fraction of sodium polyacrylate solution are mixed (the mass ratio of precipitated silica to sodium polyacrylate solution is 100:7), and ground, the grinding stirring mill host speed is set to 380r / min, the diaphragm pump feed rate is 55L / min, and the time is 80min to obtain silica slurry; wollastonite slurry and silica slurry are mixed (the mass ratio of wollastonite slurry to silica slurry is 2.7:1) and ground, the grinding stirring mill host speed is set to 500r / min, the ball-to-material ratio is 19:1, and the time is 90min to obtain a mixed slurry; the mixed slurry and high-efficiency polycarboxylic acid modifier (BASF 4930F) (the mass ratio of the mixed slurry and the high-efficiency polycarboxylic acid modifier is 100:0.8) and ground for 70 minutes to obtain a composite slurry, which is flash-dried and collected by a cyclone to obtain a composite powder with a D97 of 0.9 μm; the composite powder is fed to a horizontal gravity infrared mixing modification equipment through a spiral auger, and N-phenyl-γ-aminopropyltrimethoxysilane coupling agent is added (the mass ratio of the composite powder to the silane coupling agent is 100:1.0) for dry composite modification, and the modification temperature is set to 120°C for 60 minutes. After the modification is completed, the obtained samples are sieved, tested and packaged in sequence to obtain modified wollastonite.

[0070] The modified wollastonite prepared in this example was subjected to batch sample testing to obtain the physical property parameters of the modified wollastonite obtained in this example, as shown in Table 2.

[0071] Table 2 Physical property parameters of modified wollastonite obtained in Example 2

[0072]

[0073]

[0074] Example 3

[0075] The wollastonite ore with a particle size of 1.5 to 6 mm is roughly crushed, and then dry-ground to obtain needle-shaped wollastonite with a particle size of 5 to 10 μm and a whiteness of ≥85%;

[0076] Needle-shaped wollastonite, sodium silicate and water were mixed, and the mass ratio of wollastonite to sodium silicate was 100:1.0. During the mixing process, wollastonite, the first part of sodium silicate and water were first mixed and ground for 35 minutes, and then the remaining sodium silicate (the mass ratio of the first part of sodium silicate to all sodium silicate was 70:100) was added and ground for 55 minutes to obtain a wollastonite slurry with a solid content of 66% (the D97 of the wollastonite slurry was 1.6 μm; the wollastonite slurry was dried, and the specific surface area of ​​the dried powder was 12.5 m 2 / g, sedimentation volume is 2.9mL / g); 33% mass fraction of precipitated silica solution and 28% mass fraction of sodium polyacrylate solution are mixed (the mass ratio of precipitated silica to sodium polyacrylate solution is 100:8), and ground, the grinding stirring mill host speed is set to 360r / min, the diaphragm pump feeding rate is 50L / min, and the time is 60min to obtain silica slurry; wollastonite slurry and silica slurry (the mass ratio of wollastonite slurry to silica slurry is 3.5:1.5) are mixed and ground, the grinding stirring mill host speed is set to 560r / min, the ball-to-material ratio is 16:1, and the time is 80min to obtain a mixed slurry; the mixed slurry and silicone oil (Dow Corning silicone oil PMX200350CST) was mixed (the mass ratio of the mixed slurry and the silicone oil was 100:1) and ground for 60 minutes to obtain a composite slurry. The composite slurry was flash dried and collected by a cyclone to obtain a composite powder with a D97 of 1.1μm. The composite powder was fed to a horizontal gravity infrared mixing modification equipment through a spiral auger, and N-phenyl-γ-aminopropyltrimethoxysilane coupling agent was added (the mass ratio of the composite powder to the silane coupling agent was 100:1.1) for dry composite modification. The modification temperature was set to 100℃ and the time was 30 minutes. After the modification was completed, the obtained samples were sieved, tested and packaged in sequence to obtain modified wollastonite.

[0077] The modified wollastonite prepared in this example was subjected to batch sample testing to obtain the physical property parameters of the modified wollastonite obtained in this example, as shown in Table 3.

[0078] Table 3 Physical property parameters of modified wollastonite obtained in Example 3

[0079] batch 1 2 3 4 5 Whiteness 98.5 98.7 98.3 98.4 98.1 Oil absorption value / ml / 100g 33 32 33 33 32 D97 / μm 3.58 3.57 3.61 3.62 3.59 D50 / μm 1.55 1.56 1.57 1.61 1.59 <![CDATA[BET specific surface area / m 2 / g]]> 13.59 13.28 13.18 13.56 13.69 Activation degree / % 98.87 98.65 98.69 98.97 98.85 Moisture / % 0.18 0.16 0.23 0.21 0.17

[0080] Application Example 1

[0081] The modified wollastonite prepared in Example 1 was applied to fluororubber (wherein the basic formula of fluororubber was: 100 parts of fluororubber, 3 parts of magnesium oxide, 6 parts of calcium hydroxide, 1 part of microcrystalline wax, 20 parts of modified wollastonite prepared in Example 1, 1.8 parts of bisphenol AF, 0.7 parts of accelerator BPP and 6 parts of white carbon black; hot refining at 60° C. in an open mill, and the mixing time was 20 min), and the vulcanized rubber performance test, high temperature tensile performance test and thermal conductivity test were carried out. The determination of the tensile stress-strain property of the rubber was tested in accordance with the national standard GB / T528-2009; and the wear index of the rubber was determined using an Akron abrasion tester, and the determination method was detected in accordance with the national standard GB / T1689-2014.

[0082] Application Example 2

[0083] The other conditions in Application Example 1 remain unchanged, and the modified wollastonite prepared in Example 1 is replaced by the modified wollastonite prepared in Example 2.

[0084] Application Example 3

[0085] The other conditions in Application Example 1 remain unchanged, and the modified wollastonite prepared in Example 1 is replaced by the modified wollastonite prepared in Example 3.

[0086] Application Comparative Example 1

[0087] While keeping other conditions in Application Example 1 unchanged, the modified wollastonite prepared in Example 1 is replaced by unmodified wollastonite (the preparation method of unmodified wollastonite comprises the following steps: coarsely crushing wollastonite ore with a particle size of 1.5 to 6 mm, and then dry grinding to obtain needle-shaped wollastonite with a particle size of 5 to 10 μm and a whiteness ≥ 85%).

[0088] Application Comparative Example 2

[0089] The other conditions in Application Example 1 remain unchanged, the modified wollastonite prepared in Example 1 is not added, and the amount of white carbon black in the basic formula of fluororubber is changed to 12 parts.

[0090] The performance test results of the fluororubber containing different fillers obtained in Application Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 4; the high-temperature tensile performance and thermal conductivity test results of the fluororubber containing different fillers obtained in Application Examples 1 to 3 and Comparative Examples 1 to 2 are shown in Table 5.

[0091] Table 4 Performance test results of fluororubber containing different fillers obtained in Application Examples 1 to 3 and Comparative Examples 1 to 2

[0092]

[0093] Table 5 Test results of high temperature tensile properties and thermal conductivity of fluororubbers containing different fillers obtained in Application Examples 1 to 3 and Comparative Examples 1 to 2

[0094]

[0095]

[0096] It can be seen from Tables 4 and 5 that, under the same formulation system, the physical properties and high-temperature physical properties of the vulcanized rubber (Application Examples 1 to 3) with different modified wollastonite prepared by the present invention are significantly improved compared with the application comparison examples 1 and 2 without modified wollastonite, indicating that the modified wollastonite prepared by the present invention can be used in fluororubber and has excellent reinforcement effect.

[0097] As can be seen from the above embodiments, the present invention provides a method for preparing modified wollastonite, wherein needle-shaped wollastonite and an inorganic silicon source are mixed, and the inorganic silicon source can be used as a dispersant and an inorganic in-situ modifier, which achieves the effect of dispersion and pre-modification of wollastonite, and can improve the hardness and wear resistance of subsequent rubber composite materials, and its needle-shaped structure can play a reinforcing effect in the fluororubber system, thereby improving the physical properties of the fluororubber; in addition, after being treated with an emulsion-like organic dispersant, an organic layer of a "continuous phase" can be formed in the fluororubber system, thereby improving the thermal conductivity of the fluororubber material, and can be better applied in high-temperature environments; furthermore, after being modified with a silane coupling agent, it can act as a lubricating powder particle, hindering the formation of a carbon black-carbon black network, increasing the interaction between the carbon black and rubber matrix, and further improving the physical properties and high temperature resistance of the fluororubber. The present invention solves the bottleneck problem of weak bonding between fluororubber and inorganic materials, improves the high-temperature compression permanent deformation and thermal conductivity of fluororubber, and realizes the localization of high-performance and high-value-added wollastonite fillers.

[0098] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for preparing modified wollastonite, It is characterized in that It includes the following steps: (1) mixing wollastonite, an inorganic silicon source and water and grinding them to obtain a wollastonite slurry; (2) mixing the precipitated white carbon black solution and the sodium polyacrylate solution and grinding them to obtain white carbon black slurry; (3) mixing and grinding the wollastonite slurry and the white carbon black slurry to obtain a mixed slurry; (4) mixing the mixed slurry and the organic dispersant and grinding them to obtain a composite powder; (5) mixing the composite powder with a silane coupling agent for modification to obtain the modified wollastonite; There is no order restriction between (1) and (2).

2. The method for preparing the modified wollastonite according to claim 1, It is characterized in that The particle size of the wollastonite in step (1) is 5 to 10 μm, and the whiteness of the wollastonite is ≥ 85%; The inorganic silicon source in step (1) is sodium silicate or potassium silicate.

3. The method for preparing the modified wollastonite according to claim 1 or 2, It is characterized in that The solid content of the wollastonite slurry in step (1) is 60-70%, and the mass ratio of the wollastonite to the inorganic silicon source is 100:0.6-1.2; The grinding time in step (1) is 90 to 120 minutes, and the D97 of the wollastonite slurry is 1.5 to 2 μm.

4. The method for preparing the modified wollastonite according to claim 3, It is characterized in that In step (2), the mass fraction of the precipitated silica solution is 25-35%, the mass fraction of the sodium polyacrylate solution is 20-30%, and the mass ratio of the precipitated silica to the sodium polyacrylate solution is 100:6-9; In step (2), the main rotating speed of the stirring mill for grinding is 330-390 r / min, the feeding rate of the diaphragm pump for grinding is 40-60 L / min, and the grinding time is 60-90 min.

5. The method for preparing the modified wollastonite according to claim 4, It is characterized in that The mass ratio of the wollastonite slurry to the white carbon black slurry in step (3) is 2.5-3.5:0.5-1.5; The main rotating speed of the stirring mill for grinding in step (3) is 450-650 r / min, the grinding ball-to-material ratio is 15-20:1; and the grinding time is 60-90 min.

6. The method for preparing the modified wollastonite according to claim 5, It is characterized in that The organic dispersant in step (4) comprises one or more of polyethylene glycol, a high-efficiency polycarboxylic acid modifier and silicone oil; the mass ratio of the mixed slurry to the organic dispersant is 100:0.8-1; The grinding time in step (4) is 60 to 90 minutes, and the D97 of the composite powder is 0.8 to 1.2 μm.

7. The method for preparing the modified wollastonite according to claim 6, It is characterized in that The silane coupling agent in step (5) is N-phenyl-γ-aminopropyltrimethoxysilane coupling agent; the mass ratio of the composite powder to the silane coupling agent is 100:0.6-1.

2.

8. The method for preparing the modified wollastonite according to claim 7, It is characterized in that The modification temperature in step (5) is 80 to 120° C., and the modification time is 20 to 60 minutes.

9. Modified wollastonite prepared by the method for preparing modified wollastonite according to any one of claims 1 to 8.

10. Use of the modified wollastonite according to claim 9 in fluororubber fillers.

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